The hanging chair spring length is approx 10cm(4"), thickness of steel is 7mm(0.27"),Spring capacity over 1000lbThe swing springs are SUPER HEAVY DUTY,will absorb the shock and preserve the longevity, Reduce noise, vibration and stress,not stretch outHammock Spring is Zinc plating on the harden steel,surface electric galvanizing,Sturdy and Anti-corrosion,enhance the weather resistance and lifetime of the porch swing spring.The heavy duty spring locates between the overhead support and swing chain to provide a more comfortable, softer feel to porch swings, free-standing swings, hammocks and hammock chairs.The Spring Hook Fits Almost All porch swings Bag,Hanging Chairs,Cocoon,hanging egg chair,wicker basket Gard,Hanging Hammock Chairs,heavy bags, boxing ,yard sling swing and other any of your favorite sport